In a related-art elevator, a car and a counterweight are suspended in a hoistway by a plurality of main ropes. The main ropes are wound around a drive sheave of a hoisting machine. Then, the car and the counterweight are raised and lowered by a motor of the hoisting machine rotating the drive sheave.
An encoder for generating an incremental pulse in response to a rotation of a rotational shaft of the motor is connected to the motor. The position of the car can be detected by counting the incremental pulse from the encoder.
However, actually, the main ropes slip on the drive sheave, and the main ropes are elongated. Therefore, in the method of counting the output pulse of the encoder, a difference may be generated between a detected car position and an actual car position. In other words, when the car is intended to land on a certain floor, and the motor is controlled based on the output pulse count of the encoder so that a step between a floor surface of the car and a floor surface of a landing is zero, a landing error, namely, a step may be generated.
In contrast, there is known a method of detecting a metal plate installed at a position with a certain height from the floor surface of the landing by a detector installed on the car, thereby preventing a generation of the step. In this method, when an edge of the metal plate is detected by the detector, a remaining distance to a planned stop floor acquired based on the output pulse count of the encoder is once reset. Then, a distance (set value) from the floor surface of the landing to the installed position of the metal plate is reflected to the motor control. Note that, a region (a range of the metal plate) in which the reset is carried out is usually referred to as a door zone.
Moreover, the Building Standards Act prohibits a door open operation in a state in which the floor surface of the car and the floor surface of the landing are separated by a certain height or more. Therefore, a function of determining whether or not the position of the car is in a door open operation permission zone (re-level zone) is also necessary.
As an elevator landing position detection device having a function of detecting the edge of the identification plate such as a metal plate and a function of determining whether or not the car is in the re-level zone, for example, there are known detection devices of an optical type using an photoelectric sensor, a magnetic type using a magnetic sensor or a magnetic reed switch, an electrostatic capacitance type, an eddy current type, and a resonance coil type.
The optical type out of those types can highly precisely detect the identification plate, but has such a disadvantage as being sensitive to dust, water drops, and ambient light. In contrast, the magnetic type, the electrostatic capacitance type, the eddy current type, and the resonance coil type are excellent in environment resistance as compared to the optical type. Therefore, the types other than the optical type are generally used for switches and sensors used in a safety system for preventing a serious incident in the elevator.
For example, in a related-art car position detection device of the eddy current type, a metal conductive identification plate is installed on a guide rail for guiding raising and lowering of a car, and a detector of the eddy current type is installed on the car. Then, an output signal from the detector of the eddy current type at the time when the detector of the eddy current type is opposed to the identification plate is used to detect a position and a speed of the car (for example, refer to Patent Literature 1).